A switched map is one that, either as the result of a service-switch file or because of sendmail's internal logic, causes lookups to follow a select path. For example, Sun's Solaris 2 nsswitch.conf might specify that aliases be looked up in the order files, then nis:

switch_map_open(name, file, mode)   from -d38.2
switch_map_find => nummaps
                dbtype
                ...

First the number of database maps found is printed with nummaps, then the database type for each map found in the list is printed, such as files, or nis.